Located to the south of, and bridged to, Big Coppitt Key.

Named after the Geiger tree, Cordia Sebestena L., which in turn was named by John James Audubon for Captain Geiger, a successful Key West wrecker with whom Audubon lived during a stay in the keys. A.D. Bache, in the notes for his Coast Survey conducted in 1861 says of the key: "Geiger's Key is 2 miles long and 1 mile wide. It was in good cultivation in 1855, and was then inhabited by an industrious German, from whom it derived its name."